In the most stunning upset of the midterm election season, House Majority Leader Eric Cantor was crushed in the Virginia Republican primary Tuesday by little-known tea party-backed challenger Dave Brat.

With 100 percent of the vote counted, Brat had 55.5 percent to Cantor's 44.5 percent.

"I know there's a lot of long faces here tonight," Cantor told shocked supporters in a Richmond hotel ballroom, The Washington Post reported. "It's disappointing, sure. But I believe in this country. I believe there's opportunity around the next corner for all of us."

Cantor spoke for just four minutes, promising to continue to "fight for the conservative cause."

Brat, an economics professor who's never run for public office, has been a relentless critic of the better-financed and far-better-known Cantor — who had been considered a potential future House speaker — for spending too much time in Washington and losing touch with his conservative base at home.

He called his win a "miracle," but said it also was a clear mandate.

"I'm utterly humbled and thankful," he told Fox News Channel's Sean Hannity. "God acts through people, and God acted through the people on my behalf."

"We're just celebrating like crazy tonight, an unbelievable miracle."

Brat said, however, that he did not feel the race was "a contest between the tea party and the Republicans," adding: "I ran on the Republican principles."

"If you go door-to-door knocking, the American people know the country is headed in the wrong direction," Brat told Hannity.

Though Brat hit Cantor hard on his support for immigration reform, he said that wasn't the only issue in the race.

"It's the most symbolic issue that captures the differences between myself and Eric Cantor in this race. But it also captures the fissure between Main Street and Wall Street," he said.

In November, Brat, who teaches at Randolph-Macon College, a small liberal arts school north of Richmond, will face Democratic nominee Jack Trammell, a professor at the same college.

"I'm as stunned as anybody," said Larry Sabato, director of the Center for Politics at the University of Virginia. "I've yet to find one person nationally or in the state outside the Brat circle who thought Cantor would be beaten.

"This is one of the most stunning upsets in modern American political history," Sabato said. "This is the base rebelling against the GOP leadership in Washington, as represented by Eric Cantor.

"They are angry at the establishment. Eric Cantor represents inside Washington — and this is a repudiation of the Republican leadership strata."

Cantor, first elected in 2000, won the 2012 Republican primary with 79 percent of the vote. He has been the House majority leader since 2011, and has served in the Republican leadership since 2003.

Most Republicans view Cantor, 51, as the most conservative member of the House leadership, CNN noted, saying he served as President Barack Obama's chief foil in budget negotiations in 2011.

On the eve of the primary, Brat kept up his needling of Cantor on immigration.

"Congressman Cantor has now publicly declared his intention to pass amnesty as soon as he possibly can, with President Obama's help," Brat told The Daily Caller on the eve of the primary.

"He is working hand-in-glove with the Chamber of Commerce to boost the supply of low-wage guest workers for corporations and provide other lavish Wall Street bailouts at taxpayers' expense. No lawmaker is more beholden to large corporate funders than Eric Cantor. His corporate donors think they can buy this election."

Brat even was able to pick off some former Cantor backers, PBS reported.

"[Cantor's] interests have turned toward large corporations, and he's not looking out for my interests," Ron Hedlund, who owns a small industrial repair business in Richmond and was a former volunteer for Cantor, told PBS.

Brat had also picked up support from some local Republican groups as well, ominously topping Cantor by more than 40 points in a straw poll at the district's GOP convention in May, PBS noted.

For his part, Cantor — who collected more than $1 million in April and May for his campaign — stuck to accusations that Brat, who raised a little over $200,000, was a "liberal college professor."

Virginia is no stranger to fights between the GOP establishment and the tea party since tea party favorite Ken Cuccinelli lost last year's gubernatorial race. This year, Cantor supporters met with resistance trying to wrest control of the state party away from tea party enthusiasts, including in Cantor's Richmond-area home district.

"It does speak to the kind of restlessness of the tea party," University of Richmond political science professor Daniel Palazzolo told the Associated Press.

The Cantor loss could bode ill for one other longtime Republican incumbent, Mississippi Sen. Thad Cochran, who's facing the fight of his life against tea party-backed challenger Chris McDaniel, who slams Cochran as not conservative enough.